High powered lasers have many applications in which an intense beam of coherent light is focused onto a substrate or other target. Many high-power laser systems utilize a master oscillator power amplifier (MOPA) architecture. In a MOPA laser system a laser signal from a seed laser, referred to as a master oscillator is fed into an optical amplifier which amplifies the power of the master signal. MOPA architecture allows precise pulsing of the amplified output. MOPA-based laser systems are often used in high power applications, such as laser micromachining.
In certain laser applications it is sometimes desirable to simultaneously apply laser light to multiple locations on the target or to simultaneously process multiple targets. For example, in laser micromachining it may be advantageous to drill small and precise holes in parallel at multiple locations in order to speed up processing. One possible way to provide multiple laser beams is to split the amplified output from a single MOPA laser source. However, splitting the amplified output reduces the available power for each process operation. This can be a significant problem when there exists a minimum (or an optimum) average power and/or peak power for a particular operation. To compensate for the reduced power due to splitting of the beam, the output power of the laser source may be correspondingly increased.
It is generally difficult to significantly scale the total system output power of a multiple output head laser system without making architectural changes. Typically, the application dictates the optimum pulse duration, maximum or optimum PRF (pulse repetition frequency), pulse energy, peak power, wavelength, etc. Generally, the total system output power scales with average power. However, increasing the average power implies that either the PRF or pulse energy must be increased, or both. If the application restricts the PRF, then some sort of “pulse-picking” means would be needed to direct some pulses to one workpiece and other pulses to another workpiece. This tends to be complicated, unreliable, and/or expensive. Often the laser system puts limits on the pulse energy. Also, many laser systems put constraints on the relationships between pulse energy and other pulse parameters. Hence, it can be difficult to arbitrarily increase the power of a laser system (frequency-converted or otherwise) without compromising some of the parameters that are essential to the application.
An alternative to splitting the output of one laser system is to use multiple complete laser systems. Unfortunately, this consumes additional space, is costly and introduces performance variations because it is unlikely that the two separate lasers have identical performance characteristics. Even if identical performance could be obtained, it is difficult to synchronize the outputs from multiple laser systems.
Thus, there is a need in the art, for a multiple output laser apparatus that overcomes the above disadvantages.